Methods and systems for compressing and transmitting video signals are known in the art. Compressed digital video is largely becoming the preferred medium to transmit video to viewers everywhere. The Motion Pictures Expert Group (MPEG) specifications are standardized methods for compressing and transmitting video. In general, MPEG is used today for transmitting video over terrestrial, wireless, satellite and cable communication channels and also for storing digital video.
In accordance with the MPEG standard raw video signals are processed with motion compensation, transform coding, quantization and variable length encoding. Usually, the product of the transform coding are DCT (discrete cosine transform coefficients), the DCT coefficients of a macroblock are quantized and are represented by pairs of amplitude/runlength, whereas the runlength value indicates the number of zeroes between two non-zero coefficients. The amplitude/runlength pairs of a macroblock are coded by a variable length coding scheme to provide compressed video streams. The compressed video streams are usually segmented to packets, for allowing the transmission of the packets over a medium. The process of transforming raw video into compressed video is referred to as compression or encoding. The step of variable length encoding/decoding is also referred to as partially encoding/decoding.
Due to various constraints, such as but not limited to a limited communication channel capacity, or a limited storage space, there is a need to reduce the amount of data required to represent visual information. Various methods for performing data reduction are illustrated at U.S. Pat. No. 6,023,553 of Boyce, et al. The U.S. patent illustrates a method and apparatus for extracting intra-coded video pictures from a video bit-stream and processing the selected intra-coded video pictures to generate intra-coded video pictures suitable for use during video tape recorder (“VTR”) trick play operation.
There is a need to provide efficient methods for performing data reduction with minimal quality penalty. There is a further need to provide methods for performing fast data reduction without adding excessive delay.